Determination Of Trace Cu Research Articles

A shipboard method for catalytic kinetic spectrophotometric determination of trace Cu(II) concentrations in seawater using reverse flow injection analysis coupled with a long path length liquid waveguide capillary cell

By using reverse flow injection analysis (rFIA) and a 1.0 m liquid waveguide capillary cell (LWCC), an automatic and sensitive catalytic kinetic spectrophotometric method for on-line monitoring of Cu(II) concentrations in estuarine and coastal waters was established. Cu(II) detection was based on its catalytic effect on glutathione (GSH) oxidation by potassium ferricyanide under acidic conditions. The change in absorbance of potassium ferricyanide at 420 nm was used to monitor the reaction spectrophotometrically. Experimental parameters were optimized using a univariate experimental design approach and it was ensured that the method was free of interference from co-occurring ions such as Fe(Ⅱ), Fe(III), Mn, Zn, Cd, Al, Cr, Ni and Co. The proposed method was shown to have high sensitivity with a detection limit of 0.15 nmol L-1 in a pure water matrix and 0.23 nmol L-1 in a seawater matrix. Linearity was achieved within the range of 0.45–15 nmol L-1 in a pure water matrix and 0.69–10 nmol L-1 in a seawater matrix using a 200 cm reaction coil, while the upper limits can be extended to 40 and 25 nmol L-1, respectively, by using a shorter (100 cm) reaction coil. A high level of Cu(II) recovery was maintained, ranging between 95.2% and 101%. The relative standard deviations (RSDs) of blanks and samples spiked with 5 nmol L-1 Cu(II) standard were 1.52% (n = 13) and 1.10% (n = 13), respectively. The method was confirmed to be free of carry-over effect and a sample throughput of 26 h−1 was achieved. The method was successfully applied to underway and on-board determination of Cu(II) concentrations from a surface transect in the Jiulong Estuary and a vertical profile in the Yangtze Estuary, China, respectively.

Preparation of a novel amino functionalized ion-imprinted hybrid monolithic column for the selective extraction of trace copper followed by ICP-MS detection

In this work, a novel amino functionalized Cu(II) ion-imprinted organic-inorganic hybrid monolithic column (Cu(II)-IIHMC) was prepared via one-pot co-condensation and the combination of sol-gel and ion-imprinting techniques in a fused capillary. The Cu(II)-IIHMC was used as solid phase microextraction (SPME) matrix followed by inductively coupled plasma-mass spectrometry (ICP-MS) for the analysis of trace Cu(II). The prepared Cu(II)-IIHMC has good mechanical strength, stable imprinting sites and homogeneous structure of network skeleton with large flow-through pores by optimizing the synthesis process. Under the optimized conditions, the Cu(II)-IIHMC can selectively adsorb Cu(II) with the adsorption capacity of 3.13 mg g−1. With enrichment factor of 10-fold, the calibration curve was established in the range of 0.05–50 μg L−1 with r2 of 0.9992 and the detection limit was 0.008 μg L−1 for Cu(II). Compared with the non-imprinted hybrid monolithic column (Cu(II)-NIHMC), the Cu(II)-IIHMC possesses better selectivity, anti-interference ability and adsorption capacity. The Cu(II)-IIHMC can specifically capture the target ion in the presence of competitive ions, with the selectivity coefficients exceeding 39.4. The protocol was validated by analyzing Certified Reference Materials of standard sediment, soil and iron ore, and the results were in good agreement with certified values. Moreover, the proposed in-tube SPME procedure can not only preconcentrate trace Cu(II), but also effectively reduce the matrix effect and powerfully eliminate the interference from the main metals in real samples. Therefore, the developed SPME-ICP-MS method with facile preparation, specific selectivity, high sensitivity and efficient analysis, was applied in the determination of trace Cu(II) in environmental and mineral samples with the recoveries of 89.8–111.8% in all spiked samples.

Application of Ultrasound-assisted Cloud-point Extraction and Spectrophotometry for Preconcentration and Determination of Trace Amounts of Copper(II) in Beverages

A new method for preconcentration of trace Cu(II) in beverages before determination by spectrophotometry is presented. The method is based on the ternary complex formation of Cu(II) with Safranin T in presence of pyrogallol at pH 5.5 followed by its extraction into the micellar phase of Triton X-114. The ternary complex was monitored by spectrophotometry at 532 nm. Variables affecting extraction efficiency were evaluated and optimized. Under the optimal conditions, the detection limit was 0.6 µg/L in the range of 2–300 µg/L with sensitivity enhancement of 55 after preconcentration from 15 mL of the sample, and precision was in the range of 2.5–3.9%. The accuracy was verified by the analysis of two certified samples and recovery studies of the spiked samples. The intra- and inter-day precision varied in the ranges of 3.7–4.6 and 3.9–5.2%, respectively. The method was successfully applied to determination of trace Cu(II) in beverages.

A Novel Electrochemical Sensor Based on A Glassy Carbon Electrode Modified with GO/MnO2 for Simultaneous Determination of Trace Cu(II) and Pb(II) in Environmental Water

AbstractIn this study, manganese dioxide hybridized with graphene oxide (GO/MnO2) nanocomposite was prepared by a facile synthesis method, which was applied to modify the glassy carbon electrode (GCE) in an electrochemical sensor of Cu(II) and Pb(II) for the first time. The morphology and structure of the nanocomposite were investigated by scanning electron microscopy, transmission electron microscopy and X‐ray diffraction, which exhibited MnO2 had been uniformly attached to the lamellar structure of GO, resulting in more adsorptive sites. Electrochemical properties of GO/MnO2/GCE were characterized by cyclic voltammetry and electrochemical impedance spectroscopy and the result confirmed GO/MnO2/GCE had an excellent electrochemical performance. Furthermore, the important factors affecting on the sensor sensitivity, including pH value, deposition potential, deposition time and material proportion were systematically investigated using square wave anodic stripping voltammetry (SWASV). The interferences from other ions on the target ion have also been discussed in this study. Under the optimal conditions, the GO/MnO2/GCE exhibited the linear ranges of 0.05 ∼ 1 μM for Cu(II) and Pb(II) with the detection limits of 1.67 nM and 3.33 nM, respectively, which was much lower than some electrochemical methods in reported literatures. The work provides a novel, simple and fast method for the simultaneous determination of Cu(II) and Pb(II).

A new method for simultaneous determination of trace amounts of Cu(II) and Ni(II) ions by preconcentration and spectrophotometric analysis

Immediate preconcentration and spectrophotometric methods have been developed for the determination of trace amounts of cupric ion (Cu(II)) and nickel ion (Ni(II)) through a solid phase extraction with XAD-4-N,N'-bis-(salicylidene) cyclohexanediamine (XAD-4-SCHD) resin and a complex color reaction of the ions with 2,6-dimethyl-morpholine dithiocarbamate (DMMDTC) in Triton X-100 media. A high preconcentration factor of 125 was achieved. The spectrophotometric method was based on the measurements of the absorption of colored chelates of ions complexing with DMMDTC, and the adsorptions of the complex solutions were measured at their maximum absorption peaks at 460 and 328 nm for Cu(II) and Ni(II) ions, respectively. The impact of the complexing reaction variables including type and amount of surfactant, pH, amount of ligand, and complexation time on the sensitivity of the proposed method was optimized. Calibration graphs were found to be linear in the ranges of 0.02-3 and 0.02-2.5 mg L$^{-1}$ with detection limits of 5 and 7 $\mu $g L$^{-1}$ for Cu(II) and Ni(II), respectively. The accuracy of the developed method was calculated by recovering all Cu(II) and Ni(II) ions in synthetic and TMDA-70.2 certified reference water samples. Results of the proposed method were also compared with inductively coupled plasma-mass spectrometry results for the determination of trace Cu(II) and Ni(II) ions in water samples.

Electrochemical determination of trace copper(ii) based onl-cysteine functionalized gold nanoparticle/CdS nanosphere hybrid

This paper describes a simple and efficient electrochemical assay for the determination of trace Cu(ii) employingl-cysteine functionalized gold nanoparticles/CdS nanospheres/glassy carbon electrode (l-cys/AuNPs/CdS/GCE) as an enhanced sensing platform.

Dispersive liquid-liquid microextraction (DLLME) combined with graphite furnace atomic absorption spectrometry (GFAAS) for determination of trace Cu and Zn in water Samples

Dispersive liquid-liquid microextraction (DLLME) combined with graphite furnace atomic absorption spectrometry (GFAAS) was proposed for the determination of trace amounts of Copper and Zinc ions using 8-hydroxyquinoline (8-HQ) as chelating agent. Several factors influencing the microextraction efficiency of Cu and Zn and their subsequent determinations, such as pH, extraction and disperser solvent type and their volume, concentration of the chelating agent and extraction time were studied, and the optimized experimental conditions were established. After extraction, the enrichment factors were 25 and 26 for Cu and Zn, respectively. The detection limits of the method were 0.025 and 0.0033 μg/L for Cu and Zn, and the relative standard deviations (R.S.D) for five determinations of 1 ng/ml Cu and Zn were 8.51% and 7.41%, respectively.

Chip-based liquid phase microextraction combined with electrothermal vaporization-inductively coupled plasma mass spectrometry for trace metal determination in cell samples

Metal determination in precious biological samples is critical to metallomics research. Microfluidic chips provide an excellent platform for the miniaturization of extraction. In this work, a chip-based liquid phase microextraction (chip-based LPME) device was fabricated and combined with electrothermal vaporization-inductively coupled plasma mass spectrometry (ETV-ICP-MS) for the determination of trace Cu, Zn, Cd, Hg, Pb and Bi in cell samples and human serum samples. With sodium diethyldithiocarbamate (DDTC) as both the chemical modifier for low-temperature ETV-ICP-MS and the extracting reagent for the chip-based LPME, the chip parameters influencing the extraction efficiency including central channel width, branch channel ratio and central channel length were optimized by orthogonal design experiments. Under the optimized conditions, the limits of detection (LODs) are in the range of 6.6–89.3 pg mL−1 with the RSDs ranging from 4.23–8.15% (n = 7, c = 1 ng mL−1) for the target metal ions. The linear range covers three magnitudes with correlation coefficients higher than 0.99. The proposed method was validated by analyzing the target metal ions in certified reference materials of GBW07605 human hair and GBW09152 human serum, and metal determination in HepG2 cells, Jurkat T cells and a human serum sample were achieved with the recoveries in the range of 86.6–119%. The developed method is fast, has a low sample and reagent consumption and is highly sensitive, thus it is quite suitable for the analysis of precious biological samples such as cells.

Preconcentration and Determination of Trace Cu, Pb, and Zn in Biological Samples by Combining Carbon Nanofibers (CNFs) as a Solid Phase Extraction Adsorbent with ICP-MS

Preconcentration and Determination of Trace Cu, Pb, and Zn in Biological Samples by Combining Carbon Nanofibers (CNFs) as a Solid Phase Extraction Adsorbent with ICP-MS

Magnetic Solid-Phase Extraction Based on AAPTS/Fe3O4 Nanoparticles for the Determination of Trace Cu and Pb in Environmental Samples Coupled With Graphite Furnace Atomic Absorption Spectrometry

Magnetic Solid-Phase Extraction Based on AAPTS/Fe3O4 Nanoparticles for the Determination of Trace Cu and Pb in Environmental Samples Coupled With Graphite Furnace Atomic Absorption Spectrometry

Modification and characterization of amberlite XAD-2 with calcein blue for preconcentration and determination of copper(II) from environmental samples by atomic absorption spectroscopy

A chelating resin is produced by coupling a dye calcein blue to Amberlite XAD-2 through an azo spacer. The resulting resin has been characterized by FT-IR, elemental analysis, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) studied for the preconcentration and determination of trace Cu(II) from solution samples. The optimum pH for adsorption of copper ions was 6. The sorption capacity of functionalized resin is 27 mg·g−1. The chelating resin can be reused for 10 cycles without any significant changes in sorption capacity. A recovery of 100% was obtained for Cu(II) when eluted with 0.5 M nitric acid. Scatchard analysis revealed that homogeneous binding sites were formed in the resin. The equilibrium adsorption data of Cu(II) on modified resin were analyzed by Langmuir, Freundlich and Temkin models. Based on equilibrium adsorption data the Langmuir, Freundlich and Temkin constants were determined 0.036, 2.196 and 0.348 at pH 6 and 20 °C, respectively. The method was applied for Cu(II) assay in environmental samples.

Salicylaldoxime이 내포된 p-Dichlorobenzene 미세결정을 이용한 Cu(II)의 예비농축 및 정량

Salicylaldoxime (SA)이 내포되어 있는 미세결정 p-dichlorobenzene 흡착제(p-dichlorobenzene-SA)를 이용하여 시료에 흔적량으로 들어있는 Cu(II)를 예비농축시킨 후 불꽃 원자흡수분광법으로 정량하는 방법을 개발하였다. 시료 용액의 pH, 킬레이트제 salicylaldoxime의 양, 흡착제 p-dichlorobenzene-SA의 양 그리고 시료 용액의 흐름속도 등 여러 실험조건을 최적화하였다. 여러 공존이온에 대한 방해효과를 조사한 결과, <TEX>$CN^1$</TEX>가 다른 이온들보다 비교적 심하게 방해하였다. <TEX>$1\;{\mu}g\;mL^{-1}\;CN^-$</TEX>에 의한 방해효과는 Ni(II)를<TEX>$20\;{\mu}g\;mL^{-1}$</TEX> 되도록 조절한 결과, 완전히 제거할 수 있었다. 본 방법으로 얻은 직선 감응범위, 상관계수(<TEX>$R^2$</TEX>) 및 검출한계는 각각 <TEX>$3.0\sim100\;ng\;mL^{-1}$</TEX>, 0.9901, 및 <TEX>$3.1\;ng\;mL^{-1}$</TEX> 이었다. 본 방법을 실제 시료에 적용가능 여부를 확인하기 위해 수용액 시료(폐수, 저수지물 및 시냇물)와 식품시료(오렌지 쥬스, 생계란 및 탈지분유)에 응용하였다. 회수율은 93~104% 범위이었으며, ICP-MS를 이용하여 직접 측정한 값과 본 방법으로 측정한 값을 비교한 결과, 95% 신뢰수준에서 잘 일치하였다. 본 방법을 쌀가루 인증표준물질(certified reference material, CRM) 시료에 응용해 보았으며 좋은 결과를 얻었다. 실험 결과들로부터 본 방법은 여러 실제 시료에 들어있는 Cu(II)를 농축 및 정량하는데 응용할 수 있음을 확인하였다. A technique for the determination of trace Cu(II) in various real samples by FAAS after the column preconcentration onto p-dichlorobenzene-SA adsorbent, which is microcrystalline p-dichlorobenzene loaded with salicylaldoxime (SA) has been developed. Several experimental conditions such as pH of the sample solution, the amount of chelating agent salicylaldoxime, the amount of adsorbent p-dichlorobenzene-SA, and flow rate of sample solution were optimized. The interfering effects of various concomitant ions were investigated. <TEX>$CN^-$</TEX> interfered more seriously than any other ions. However, the interference by <TEX>$1\;{\mu}g\;mL^{-1}\;CN^-$</TEX> could be overcome completely by controlling the concentration of Ni(II) to <TEX>$20\;{\mu}g\;mL^{-1}$</TEX>. The linear range, correlation coefficient (<TEX>$R^2$</TEX>) and detection limit obtained by this technique were <TEX>$3.0\sim100\;ng\;mL^{-1}$</TEX>, 0.9901, and <TEX>$3.1\;ng\;mL^{-1}$</TEX>, respectively. For validating this technique, the aqueous samples (wastewater, reservoir water and stream water) and the food samples (orange juice, fresh egg and skim milk) were used. Recovery yields of 93~104% were obtained. These measured mean values were not differents from ICP-MS data at 95% confidence level. The good results were obtained from the experiments using the rice flour certified reference material (CRM) sample. Based on the experimental results, it was found that this technique could be applied to the preconcentration and determination of Cu(II) for various real samples.

Determination of trace copper in food samples by flame atomic absorption spectrometry after solid phase extraction on modified soybean hull

Soybean hull was chemically modified with citric acid and used as a solid phase extraction adsorbent for the determination of trace amounts of Cu 2+ in food samples by flame absorption spectrometry (FAAS). The effect of pH, sample flow rate and volume, elution flow rate and volume and co-existing ions on the recovery of the analyte were investigated. The results showed that Cu 2+ could be adsorbed on the modified soybean hull at pH 8.0 and eluted by 2.0 mL of 1.0 mol L −1 HCl. Under the optimized conditions, the adsorption capacity of modified soybean hull was found to be 18.0 mg g −1 for Cu 2+. The detection limit of the proposed method was 0.8 ng mL −1 for Cu 2+ with an enrichment factor of 18. The analytical result for the certified reference tea sample (GBW07605) was in a good agreement with the certified value. The proposed method has also been successfully applied to the determination of trace Cu 2+ in dried sweet potato, lake water and milk powder, the recovery of Cu 2+ for spiked samples was between 91% and 109.6%.

Solid-phase extraction of Cu, Co and Pb on oxidized single-walled carbon nanotubes and their determination by inductively coupled plasma mass spectrometry

A novel method using a microcolumn packed with single-walled carbon nanotubes (SWNTs) as a new adsorption material was developed for the preconcentration of trace Cu, Co and Pb in biological and environmental samples prior to their determination by inductively coupled plasma mass spectrometry (ICP-MS). SWNTs oxidized with concentrated nitric acid have been proved to possess an exceptional adsorption capability for the analytes due to their surface functionalization. The adsorption behaviors of the analytes on SWNTs under dynamic conditions were studied systematically. The main factors influencing the preconcentration and determination of the analytes (pH, sample flow rate and volume, eluent concentration and interfering ions) have been examined in detail. Under the optimum conditions, the detection limits for Cu, Co and Pb were 39, 1.2 and 5.4 pg mL −1, respectively; the relative standard deviations (RSDs) were found to be less than 6.0% ( n = 9, c = 1.0 ng mL −1). This method was validated using a certified reference material of mussel, and has been successfully applied for the determination of trace Cu, Co and Pb in real water sample with the recoveries of 96.0–109%.

Study on Solvent Extraction Using Salen(NEt2)2as a Chelating Agent for Determination of Trace Cu(II), Mn(II), and Zn(II) in Water Samples

Solvent extraction using a Schiff-base, salen<TEX>$(NEt_2)_2$</TEX>, as a chelating agent has been conducted on several water samples to study the determination of trace Cu(II), Mn(II) and Zn(II). Experimental conditions for the formation and extraction of metal complexes were optimized with an aqueous solution similar in composition to the samples. The matrix difference between the sample and standard solutions was approximately matched, and the pH of each sample solution was adjusted to 9.5 with <TEX>$NaHCO_3/NaOH$</TEX> buffer. The concentration of salen<TEX>$(NEt_2)_2$</TEX> was <TEX>$7.3\;{\times}\;10^{-3}$</TEX> mol/L, and the complexes were extracted into MIBK solvent followed by the measurement of AAS absorbance. The potential interference of concomitant ions was investigated, but no interference from alkaline and alkali earth ions was shown in this procedure. The given procedure is precise, as judged from the relative standard deviation of less than 5% for five measured data. The recovery of 93-103% shows that this method is quantitative for such trace metal analysis.

Room temperature ionic liquids enhanced chemical vapor generation of copper, silver and gold following reduction in acidified aqueous solution with KBH4 for atomic fluorescence spectrometry

Room temperature ionic liquids (RTILs), as novel solvents, have many fascinating properties which make them of fundamental interest to all chemists. Herein, we report the first application of an RTIL in the chemical vapor generation (CVG) of transition and noble metals following reduction of acidified analyte solution with KBH4. Copper, silver and gold were selected as model analytes, and N-butylpyridinium tetrafluoroborate ([N bupy][BF4]) was used as a model RTIL. The RTIL-enhanced CVG of copper, silver and gold was evaluated by flow injection atomic fluorescence spectrometry (FI-AFS). The addition of [N bupy][BF4] leads to a 4.8-, 2.7- and 3.6-times improvement in the CVG efficiencies for copper, silver and gold, respectively. Interference from Zn(II), Fe(III), Co(II), Ni(II), Pb(II), Se(IV) and As(III) was also reduced in the presence of [N bupy][BF4]. The role of the RTIL was supposed to be inhibition of further coalescence of the metal nanoparticles which may constitute the volatile metal species leaving the solution and/or reaching the atomizer, and hence prevention of the loss of volatile metal species. With the consumption of a 0.5 mL sample solution, the detection limits (3s) for Cu, Ag and Au are 19, 15 and 6.3 μg L−1, respectively. The precisions (RSD, n = 11) for eleven replicate measurements of the standard solution containing 50 μg L−1Cu, Ag and Au were 4.4%, 5.2% and 4.7%, respectively. The developed RTIL-enhanced FI-CVG-AFS method was successfully applied to determination of trace Cu, Ag and Au in several certified biological and geological reference materials.

Determination of copper(II) in various samples by flame atomic absorption spectrophotometry after column preconcentration onto pulverized Amberlite XAD-4 loaded with N-benzoylphenylhydroxylamine

A sensitive technique for the determination of trace Cu(II) in various samples after column preconcentration by adsorbing onto pulverized Amberlite XAD-4 loaded with N-benzoylphenylhydroxylamine (BPHA) was developed. Several experimental conditions, such as the size of XAD-4, adsorption flow rate, pH of sample solution, and so forth, were optimized. The interfering effects of diverse concomitant ions were investigated. Al(III), Fe(III), Ni(II), and Co(II) interfered, but the interference by these ions was completely eliminated by adjusting the amount of XAD-4-BPHA resin to 0.30 g. The dynamic range, the correlation coefficient (R2), and the detection limit obtained by the proposed technique were 1.0–60, 0.9953, and 0.83 ng/mL, respectively. For validating the technique, the aqueous samples (stream water, reservoir water, and wastewater), the diluted brass sample, and the plastic sample were used as real samples. Recovery yields of 94–102% were obtained. These measured data were not different from ICP-MS data at the 95% confidence level. This method was also validated by rice flour CRM (normal, fortified) samples. Based on the results of the experiment, it has been found that the proposed technique can be applied to the determination of Cu(II) in various real samples.

Hollow‐fiber liquid‐phase microextraction prior to low‐temperature electrothermal vaporization ICP‐MS for trace element analysis in environmental and biological samples

A new method of hollow-fiber liquid-phase microextraction (HF-LPME) prior to electrothermal vaporization (ETV) inductively coupled plasma mass spectrometry (ICP-MS) determination of trace Cu, Zn, Pd, Cd, Hg, Pb and Bi, based on gaseous compounds introduction into the plasma as their diethyldithiocarbmate (DDTC) chelates, was developed. The use of the reagent DDTC as chemical modifier could not only enhance the analytical signals, but also decrease the vaporization temperature. At a temperature of 1300 degrees C, trace Cu, Zn, Pd, Cd, Hg, Pb and Bi can be vaporized completely into the ICP. The factors affecting the formation of the chelates and their vaporization behaviors were investigated in detail, and the microextraction conditions were optimized. Under the optimized conditions, the detection limits of the proposed method were 12.4, 28.7, 7.9, 4.5, 3.3, 4.8 and 1.6 pg ml(-1) for Cu, Zn, Pd, Cd, Hg, Pb and Bi, respectively. Enrichment factors of 305, 284, 24, 29, 20, 73 and 43 could be achieved within 15 min of extraction time, and the relative standard deviations (RSDs) for the seven determinations of 0.5 ng ml(-1) of target analytes were 8.8, 6.9, 7.1, 9.4, 10.2, 6.1 and 10.8%, respectively. The newly developed method has been applied to the determination of trace Cu, Zn, Pd, Cd, Hg, Pb and Bi in environmental water and human serum samples, and the recoveries for the spiked samples were in the range of 88-116%. In order to validate this method, two certified reference materials, GBW08501 peach leaves and GBW(E)080040 seawater, were analyzed, and the determined values were in good agreement with the certified values.

Characterization, growth mechanism and application of network poly(bromophenol blue)

Abstract Network poly(bromophenol blue) (denoted as PBPB) films were electrochemically synthesized on the surface of glassy carbon electrode (GCE) by cyclic voltammetry and then the chemically modified electrode (denoted as PBPB-GCE) was fabricated. The characterization and growth mechanism of electrochemically synthesized PBPB films were firstly investigated by attenuated total reflection (ATR)-FTIR spectroscopy, in situ electron spin resonance (ESR) spectroelectrochemistry, qualitative analysis and electrochemical methods. This PBPB-GCE was successfully used to develop a novel and reliable electrochemical method for the determination of trace Cu 2+ by anodic stripping voltammetry. Based on the results from cyclic voltammograms or differential pulse voltammograms, the modified electrode showed excellent sensitivity toward the determination of Cu 2+ in H 2 SO 4 solution (pH 2.0). Under the optimized working conditions, there was a good linear relationship between anodic peak current and Cu 2+ concentration in the range of 1.0 × 10 −8 –1.0 × 10 −5 M with the detection limit of 3.5 × 10 −9 M (S/N = 3) in H 2 SO 4 solution (pH 2.0). The current responses of successive measurements at the identical surface ( n = 30) and at the renewed ones ( n = 10) of PBPB-GCE were examined with relative standard deviation of 2.8% and 4.1%, respectively. It indicated that the chemically modified electrode showed good stability and reproducibility. The interference studies showed that the modified electrode exhibited excellent selectivity in the presence of other metal ions with a concentration much higher than that of Cu 2+ . In the end, this proposed method was successfully applied to determine the concentration of Cu 2+ in water samples.

A selective fluorescence-on reaction of spiro form fluorescein hydrazide with Cu(II)

The spiro form fluorescein hydrazide ( 1) bearing a cleavable active bond is characterized as a highly selective and sensitive fluorescence probe for Cu 2+. In 0.01 M Tris–HCl buffer (pH 7.2), the probe displays a highly selective fluorescence-on response to Cu 2+ only, instead of other common metal ions. The reaction mechanism has been explored and proposed as that the hydrazide group of 1 recognizes and binds Cu 2+, and the subsequent complexation of Cu 2+ promotes hydrolytic cleavage of the amide bond, causing the release of fluorophore (fluorescein) and thereby the retrievement of fluorescence. Conditions for fluorescence measurement were optimized, generating a calibration curve that is linear over the concentration range of 0.1–10 μM Cu 2+. The detection limit for Cu 2+ is 64 nM based on 11 blank determinations ( k = 3), also showing a highly sensitive feature. The fluorescence-on reaction described here has been used for the determination of trace Cu 2+ in real biological fluids with satisfactory results.